In recent years, LEDs have begun to be used as light sources for illumination. Conventional LED modules have a structure in which an electrode pattern is formed on a non-conductive circuit board that is made from glass epoxy resin or the like, and a reflective cup portion is provided that is used to efficiently reflect light emitted from an LED in a forward direction. An LED element is mounted on the bottom surface of this  reflective cup portion, and the reflective cup portion is then sealed with resin using a transparent resin having a high refractive index.
When an LED is turned on, power which does not contribute to light emission is converted into heat. In order to use an LED for illumination, it is necessary to package a number of LED on a substrate, and supply a considerable amount of power thereto. Because of this, a mounting substrate which exhibits an excellent heat dissipation performance is required. However, when a circuit board that is formed from glass epoxy resin, which is typically used conventionally, is used as a substrate for mounting LED for illumination, because the heat dissipation performance of this substrate is poor, the temperature of the LED is increased by the generated heat and the problem arises that there is a deterioration in the light emitting efficiency of the LED.
Conventionally, the structure described in Patent Document 1 has been proposed as a circuit board structure having a good heat dissipation performance. This is a structure in which, in order to improve the heat dissipation performance of the substrate, a heat dissipation metal plate is connected to an exposed surface of the substrate core material. However, the technology described in Patent document 1 is intended to provide protection from the effects of heat when circuit components such as IC are mounted at a high density, and there is no description of its use as an illumination apparatus or of any usage of LED.
Patent document 1: Unexamined Japanese Patent Application, First Publication No. S64-28886